Recovery and use of conjunct polymers from ionic liquid catalysts

ABSTRACT

A process comprising regenerating a used ionic liquid catalyst, recovering conjunct polymer from the regenerated catalyst and using at least a portion of the conjunct polymer is disclosed.

FIELD OF THE INVENTION

The present invention relates to methods of recovery and use of conjunctpolymers derived from the use of ionic liquid catalysts. It also relatesto new hydrocarbon product compositions comprising conjunct polymers.

BACKGROUND OF THE INVENTION

Conjunct polymers are common by-products of acid-catalyzed alkylationreactions including the alkylations of isoparaffins, e.g. isobutane andisopentane, with light olefins, e.g. propylene and butenes, to producehigh octane and clean burning alkylate gasoline. The term conjunctpolymer was first used by Pines and Ipatieff to distinguish thesepolymeric molecules from typical polymers. Unlike typical polymers whichare compounds formed from repeating unites of smaller molecules bycontrolled or semi-controlled polymerizations, “conjunct polymers” are“pseudo-polymeric” compounds formed asymmetrically from two or morereacting units by concurrent acid-catalyzed transformations includingpolymerization, alkylation, cyclization, additions, eliminations andhydride transfer reactions. Consequently, the produced“pseudo-polymeric” may include a large number of compounds with varyingstructures and substitution patterns. The skeletal structures of“conjunct polymers”, therefore, range from the very simple linearmolecules to very complex multi-feature molecules.

Some examples of the likely polymeric species were reported by Miron etal. (Journal of Chemical and Engineering Data, 1963) and Pines (Chem.Tech, 1982). Conjunct polymers are also commonly known to those in therefining industry as “red oils” due to their reddish-amber color or“acid-soluble oils” due to their high uptake in the catalyst phase whereparaffinic products and hydrocarbons with low olefinicity and lowfunctional groups are usually immiscible in the catalyst phase. In thisapplication, the term “conjunct polymers” also includes ASOs(acid-soluble-oils) red oils and C₁₂+ polyalkylates.

Separating conjunct polymers formed as by-products during HF-catalyzedisoparaffin/olefin alkylation from the catalyst-alkylationproducts-conjunct polymer mixture has been described in U.S. Pat. No.5,382,746.

SUMMARY OF THE INVENTION

The present invention relates to a process comprising regenerating aused ionic liquid catalyst, recovering conjunct polymer from theregenerated catalyst and using at least a portion of the conjunctpolymer.

DETAILED DESCRIPTION

Conjunct polymers formation is inevitable during alkylation reactions ofisoparaffins with olefins to make alkylate gasoline. The formation ofconjunct polymers during alkylations is undesirable because conjunctpolymers negatively affect the overall alkylation process in many ways.They affect the yield of the desired reactions and adversely influencethe course of the intended transformations. The most significant effectof “conjunct polymers” is the role they play in the deactivation processof the catalyst.

In the alkylation processes catalyzed by sulfuric or hydrofluoric acid,conjunct polymers play a major role in the deactivation process leavingthe catalyst ineffective for alkylation at conjunct polymersconcentration of higher than 10-15 wt %. Conjunct polymers alsodeactivate other alkylation catalysts, including solid acid alkylationcatalysts. See US 20080087574A2. In sulfuric acid-catalyzed processes,the conjunct polymers are inseparable from the acid phase and verydifficult to isolate. The spent acid streams of sulfuric acid alkylationprocesses containing conjunct polymers are usually incinerated torecover sulfuric acid in the form of sulfur oxides while the hydrocarbonby-products (conjunct polymers) are burnt off. For HF alkylation, usedHF acid is heated at an elevated temperature to thermally crack thepolymer to recover HF and hydrocarbon. Stripping of light hydrocarbonand HF in the regenerator produces a complex mixture of conjunctpolymers containing heavy organic fluoride and HF. Due to toxicity of HFand corrosivity of HF containing conjunct polymer, the polymer is oftenincinerated.

Conjunct polymer formation similarly affects the performance of ionicliquid catalysts. Unlike conjunct polymers formed using HF and sulfuricacid catalysts, conjunct polymers produced in ionic liquid alkylationsare recoverable from the catalyst phase with no residual acidcontaminants and can be readily sent to processing units in the refineryto be processed into lighter or more usable cuts. This desirable featureof the recoverability of the ionic liquids-based conjunct polymersderives from the regenerability of the ionic liquid catalyst which islacking in sulfuric acid alkylation and more difficult in the HF-basedalkylation. In an embodiment, conjunct polymers are recovered from ionicliquid catalyst through the catalyst regeneration process.

Ionic liquids can be defined as liquids whose make-up is entirelycomprised of ions as a combination of cations and anions. The mostcommon ionic liquids are those prepared from organic-based cations andinorganic or organic anions. The most common organic cations areammonium cations, but phosphonium and sulphonium cations are alsofrequently used. Ionic liquids of pyridinium and imidazolium are perhapsthe most commonly used cations. Anions include, but not limited to, BF₄⁻, PF₆ ⁻, haloaluminates such as Al₂Cl₇ ⁻and Al₂Br₇ ⁻, [(CF₃SO₂)₂N)]⁻,alkyl sulphates (RSO₃ ⁻), carboxylates (RCO₂ ⁻) and many other. The mostcatalytically interesting ionic liquids for acid catalysis are thosederived from ammonium halides and Lewis acids (such as AlCl₃, TiCl₄,SnCl₄, FeCl₃). Chloroaluminate ionic liquids may be the most commonlyused ionic liquid catalyst systems for acid-catalyzed reactions, such asalkylations.

Ionic liquids may be suitable for use as catalysts and solvents for anumber of transformations including, among others, alkylation,polymerization, dimerization, oligomerization, acylation, metatheses,copolymerization, isomerization, hydrogenation, hydroformylationreactions and combinations thereof.

In one embodiment, conjunct polymer is recovered in a process forisoparaffins-olefins alkylation using butyl pyridiniumchloroaluminate-based ionic liquid catalyst co-catalyzed with HCl ort-butyl chloride to produce alkylate gasoline. During the alkylationprocess, conjunct polymers are produced. Conjunct polymers play a majorrole in the deactivation processes of the ionic liquid catalyst. In anembodiment, conjunct polymers are recovered during regeneration of theionic liquid catalyst. Regeneration of the ionic liquid catalyst forconjunct polymer recovery may be conducted by any method which freesconjunct polymer from the catalyst. Exemplary suitable methods aredisclosed in U.S. Patent Applications 20070249486; 20070249485;20070142211; 20070142213; 20070142214; 20070142215; 20070142216;20070142217; and 20070142218, which are incorporated by referenceherein.

Conjunct polymers can be recovered and extracted from the spent catalystby means of hydrolysis. The hydrolysis recovery methods employprocedures that lead to complete recovery of the conjunct polymers andare generally used for analytical and characterization purposes becauseit results in the destruction of the catalyst. Hydrolysis of the spentcatalyst is done, for example, by stirring the spent catalyst in thepresence of excess amount of water followed by extraction with lowboiling hydrocarbon solvents such as pentane or hexane. In thehydrolysis process, the catalyst salt and other salts formed duringhydrolysis go into the aqueous layer while conjunct polymers go into theorganic solvent. The low boiling solvent containing the conjunctpolymers are concentrated on a rotary evaporator under vacuum andmoderate temperature to remove the extractant, leaving behind the highboiling residual oils (conjunct polymers) which are collected andanalyzed. The low boiling extractants can be also removed bydistillation methods.

Generally, conjunct polymers recovered by hydrolysis of a butylpyridinium chloroaluminate-based ionic liquid catalyst used in a processfor isoparaffins-olefins alkylation are viscous brown odoroushydrocarbons. They are highly unsaturated molecules containing bothcyclic and acyclic features. They contain about ppm-0.8% chlorides, andmay contain up to few hundreds ppm level of sulfur (coming from thesulfur impurities in the feed). They have a boiling range of about 177°C. (350° F.) to about 593° C. (1100° F.) and a carbon number range ofabout C9 to about mid C30s. Regeneration-based conjunct polymers,recovered from a butyl pyridinium chloroaluminate-based ionic liquidcatalyst used in a process for isoparaffins-olefins alkylation, containhigh degree of unsaturation, but are less viscous, less odorous, andlighter in color than hydrolysis conjunct polymers. They exhibit aboiling range of about 350° F. to about 1100° F. and a carbondistribution of about C9 to about C30s. In an embodiment, conjunctpolymers are upgraded and refined to more useful products by sendingthem to refining/processing units.

Unlike the current alkylation processes catalyzed by HF or H₂SO₄, ionicliquid catalysts can be regenerated in such a way that the conjunctpolymers are easily extracted and recovered from the catalyst phase, andrecycled to the refinery. Conjunct polymers obtained from theregenerated catalyst are, in general, less viscous than conjunctpolymers-by-hydrolysis and lighter in color. Their color ranges fromfaint yellow to light orange. When Al/HCl or Al—Ni alloy/hydrogen, areused for the regeneration, the recovered conjunct polymers are evenlighter and, usually, colorless. Unlike the current alkylationtechnologies catalyzed by sulfuric or hydrofluoric acid, conjunctpolymers produced by ionic liquids-based catalysis are recoverable bybenefit of the catalyst regeneration, and can be used in many ways. Theconjunct polymers recovered from regeneration of ionic liquid catalystscan be readily sent to processing units in the refinery to be processedinto lighter cuts. In an embodiment, conjunct polymers can be recoveredfrom ionic liquid catalyst through the catalyst regeneration process. Inan embodiment, the recovered hydrocarbons exhibit a boiling range(simulated distillation analysis) of upper 300-1000° F. The liberatedconjunct polymers do exhibit a higher viscosity than those desired fordiesel fuel stocks. They have a VI (viscosity Index) of ˜24 and aKinematic Viscosity of 10.3 mm²/s @ 40° C. and 2.8 mm²/s @ 100° C.Hydrolysis conjunct polymers and regeneration conjunct polymers that arederived from ionic liquids-based alkylation can be readily upgraded. Theproperties of the conjunct polymers recovered by regeneration, however,are much more attractive than those of conjunct polymers recovered fromunregenerated spent catalyst streams which are more viscous and richerin organic chlorides. Table 1 shows some comparison between thehydrolysis-derived and regeneration-derived conjunct polymers.

TABLE 1 Conjunct polymers K. Vis.@ 40° C. K. Vis.@ 100° C. ColorHydrolysis CPs   26 mm²/s 3.8 mm²/s Dark Brown Regeneration CPs 10.31mm²/s 2.4 mm²/s Yellow- brown

The conjunct polymers recovered from ionic liquid alkylations can bereadily de-chlorinated and de-sulfurized by known processes in the artto transform them into more suitable feeds for the appropriate refiningor processing units. In an embodiment, these conjunct polymers aretreated to remove any impurities especially chloride impurities torender them suitable for introduction into a hydrocracker or otherprocessing unit that may be very sensitive to chlorides. These conjunctpolymers in some embodiments after dechlorination and desulfurizationmay be fed into a hydrocracker, hydrotreater, FCC unit, coker or a crudeoil unit where they can be processed into more useful products orlighter cuts. Therefore, unlike the H₂SO₄ or HF-catalyzed alkylationprocesses where the alkylation by-products are treated as waste, or mayrequire extensive clean up and pretreatment processing, the ionicliquid-derived conjunct polymers, regardless of the recovery method, aremuch cleaner than those of other alkylation technologies and requiremuch less rigorous upgrading processes. The ionic liquids-based conjunctpolymers can be readily converted into high quality light products withminimal pretreatment. So in an embodiment in which an ionic liquidcatalyst is used for low molecular weight isoparaffin olefin alkylation,the process is expanded from a process in which low molecular weightgases are converted to high quality alkylate gasoline to a process inwhich low molecular weight gases are converted to high quality alkylategasoline and in which heavier byproducts can be recycled and processedinto useful products. In essence, this embodiment is a process where lowvalue gases are converted to valued liquid products without hydrocarbonlosses. By the same token, the regeneration aspect of this embodiment isnot solely a catalyst regeneration process to reactivate the catalyst,but also an efficient procedure for pre-treating and recoveringhydrocarbon by-products which otherwise go to the waste stream.

Hydrotreating using a hydrogenation catalyst or hot caustic treating iseffective in lowering the S and Cl content. Suitable hydrotreatingcatalysts include Group VI and VIII metals and combinations dispersed onporous high surface area supports. Examples are palladium on carbon, anickel-aluminum alloy, palladium on alumina, NiMo on alumina, CoMo onalumina catalyst, or NiW on alumina. For caustic treating, Group I andGroup II metal hydroxide solutions will be effective such as NaOH, KOH,CsOH, RbOH, Mg(OH)₂, Ba(OH)₂.

Recovered conjunct polymers can be used in the production of hydrocarbonproducts such as fuels and lubricants. More specifically, recoveredconjunct polymers may be used to produce diesel fuel, jet fuel and highenergy fuels. Rather than sending recovered conjunct polymers to arefinery processing unit, they can be simply treated by procedures knownin the art to remove any residual alkyl chlorides and sulfur-basedimpurities to upgrade them to more useful products. For example, theseconjunct polymers can be hydrotreated according to procedures known inthe art to be de-chlorinated, saturated and de-sulfurized to produceclean middle distillate fuels and diesel. Fractionation of conjunctpolymers recovered from regenerated catalyst by distillation yielded upto 69% jet fuels with smoke point of 37 and extremely freezing point,25% diesel fuels with Cetane Index of 58 and no cloud point, and 6%residue suitable for the FCC unit. These conjunct polymeric species docontain cyclic systems and extensive branching that they may be used ashigh energy fuels. Both the jet fuel fraction and the diesel fuelfraction exhibit high Gravimetric Net Heat of combustion at 18880KBTU/lb and 18661 KTBU/lb, respectively.

The following Examples are illustrative of the present invention, butare not intended to limit the invention in any way beyond what iscontained in the claims which follow.

EXAMPLE 1

This Example describes a methods used to regenerate catalyst and removeconjunct polymers from the catalyst by treating the spent catalyst withaluminum metal at moderate temperatures. Spent catalyst is heated to100° C., and then allowed to stir in the presence of aluminum for agiven period of time ranging from 30-120 minutes. The reaction isnormally done in the presence of an inert hydrocarbon solvent such asnormal paraffins, such as n-hexane, to act as solvents and carriers forthe liberated conjunct polymers. The addition of hydrocarbon solvents issometimes delayed until after the aluminum treatment. Once the reactionbetween the spent catalyst containing conjunct polymers and aluminum isdone, the hydrocarbon (solvent) layer, which contains the liberatedconjunct polymer, is decanted off. The catalyst is usually rinsed withadditional amount of solvent to extract all recoverable conjunctpolymers from the catalyst phase. The solvent extracts are concentratedunder vacuum and moderate temperatures to remove the solvent. Theresidual oils (liberated conjunct polymers) are collected and analyzed.

The recovered conjunct polymers have a flash point of about 64° C. and adensity of about 0.87 gm/cc at 15° C. On the average, conjunct polymershave a specific gravity of about 0.84. The conjunct polymers have aboiling range in the range from about 350 to about 1200 deg F. Theliberated conjunct polymers do exhibit a VI (viscosity Index) of 24 andKinematic Viscosity of 10.3 mm²/s@ 40° C. and 2.4 mm²/s@ 100° C.

TABLE 2 Conjunct polymers Vis_(40° C.) Vis_(100° C.) color HydrolysisCPs   26 mm²/s 3.8 mm²/s Dark Brown Regeneration CPs 10.31 mm²/s 2.4mm²/s Yellow-brown

EXAMPLE 2 Hydrotreating of Conjunct Polymers

A 300 cc autoclave was charged with 168 gm of conjunct polymersrecovered from regenerated ionic liquid catalyst. The conjunct polymerscontained 493 ppm chlorine (organic chlorides), 69 ppm sulfur and had abromine number of 203. Then, 5-10 gm of hydrogenation catalyst was addedto the conjunct polymers in the autoclave. The autoclave was thenpressurized with hydrogen to 500 psi and heated to 200° C. and kept at200° C. while being stirred for 2 hrs. The pressure was kept at 500 psifor the duration of the run. Then, the reactor was cooled down,de-pressurized and the contents were analyzed. The reaction was donerepeatedly but with different hydrogenation catalyst each time. Thetable below shows the results as a function of the hydrogenationcatalyst. The data in the table below shows that conjunct polymers canbe readily upgraded to hydrocarbon with very minimal chloride and sulfurimpurities where they can be used as feedstocks in some of the refiningoperations such the hydrocracker diesel hydrotreater, coker, fluidcatalytic cracker or the crude oil unit.

TABLE 3 Br₂# Sulfur Chloride Starting material 30 147 ppm  361 ppm  60%Ni on Kieselguhr 28 22 ppm 10 ppm Pt/C¹ 32 74 ppm 8.8 ppm  Pd/C² 27 86ppm 33 ppm 1:1 Pt_(/c)/Pd_(/c) ³ 28 81 ppm 15.2 ppm   66%Ni-Silica/Alumina 14  9 ppm  6 ppm Pt/Pd-Silica/Alumina⁴ 172 ppm 49 ppm21 ppm (203)* (69)* (493)* *the conjunct polymers for this run were fromdifferent lot and the values in ( ) are before treatment; ¹1% Pd oncarbon 4-8 mesh; ²1% Pt on carbon 30-150 mesh; ³a mixture of 1% Pd/C and1% Pt/C; ⁴silica-alumina impregnated with Pt and Pd

EXAMPLE 3 De-Chlorination of Conjunct Polymers by Hot Caustic Treatment

In 1-liter glass reaction flask equipped with a reflux condenser and anover-head stirrer, conjunct polymers recovered from the regeneratedionic liquid catalyst were refluxed (heated at reflux) in variousaqueous KOH solutions for 2-3 hrs. Then, the reaction mixture was cooledto room temperature and the hydrocarbon was separated from the aqueouslayer and dried over magnesium sulfate. The organic phase was thenanalyzed for chlorides and sulfur contents and for olefinicity bybromine number analysis. The table below compares the conjunct polymersbefore and after the KOH treatment at different KOH strengths.

TABLE 4 Br₂# Sulfur Chloride Starting material 30 147 ppm 361 ppm 1M KOH33 132 ppm 114 ppm treatment 2M KOH 32 108 ppm 106 ppm treatment 3M KOH61 (56)* 196 (254)* ppm 144 (370)* ppm treatment 5M KOH 32 100 116 ppmtreatment *the conjunct polymers for this run were from a different lotand the values in Parentheses are before treatment

EXAMPLE 4

To de-chlorinate the conjunct polymers, they were treated with hotcaustic by heating the conjunct polymers to reflux in an aqueoushydroxide ion solution. In an aspect, this aqueous hydroxide ionsolution was 3M aqueous KOH solution. The reflux was carried out for 2-3hours. The treatment resulted in 65% chloride reduction. The treatmentwith hot 3M KOH also resulted in some de-sulfurization of the conjunctpolymers where sulfur levels dropped by ˜23-33%. Table 5 below shows acomparison between the levels of chloride and sulfur before and afterthe hot caustic treatment. There was slight upward shift in the brominenumber reflecting the elimination of hydrochloride which leads to makingmore double bonds.

TABLE 5 Run 1 Run2 Chloride before KOH 370 351 Chloride after KOH 144120 Sulfur Before KOH 254 143 Sulfur after KOH 196 95 Bromine# beforeKOH 58 30 Bromine# after KOH 62 33 Color before KOH Dark Amber Darkamber Color after KOH Light Amber Dark amber

EXAMPLE 5 Saturation of the Double bonds of Conjunct Polymers

An alternative procedure that might affect the saturation of the doublebonds of the conjunct polymers and de-chlorinate them is hydrotreatmentwith a hydrotreating catalyst. To achieve this, the conjunct polymers(75 gm) were heated at 200° C. and 500 psi H₂ pressure overhydro-processing catalyst (10 gm of alumina/silica-based hydroprocessingcatalyst impregnated with 0.18% Pt and 0.36% Pd) for 2 hrs. The reactionwas done in a 300 cc sealed autoclave (batch type reactor). The conjunctpolymers were analyzed before and after the reaction. The data issummarized in table 1 below. Hydrotreating the conjunct polymers did notresult in substantial reduction of the olefinicity of the conjunctpolymers, but reduced the chloride content by ˜95%. The sulfur contentwas also reduced by ˜29%. Noticeably, the color of the conjunctpolymers, however, changed to much lighter tint oils after thehydrotreatment. Reduction of the olefinicity of the conjunct polymers isnot an issue of concern especially since these species will be used asfeed stocks to processing units rather than end products. However, theremoval of chloride and sulfur impurities is an issue depending on whatprocessing unit these by-products will feed into.

TABLE 6 Run 1 Run2 Chloride before hydrotreatment 493 ppm  270 ppmChloride after hydrotreatment 21 ppm  15 ppm Sulfur beforehydrotreatment 69 ppm 143 ppm Sulfur after hydrotreatment 49 ppm  71 ppmBr₂# before hydrotreatment 203 30 Br₂# after hydrotreatment 172 24 Colorbefore hydrotreatment amber yellow Color after hydrotreatment Lightclear yellow

There are numerous variations on the present invention which arepossible in light of the teachings and supporting examples describedherein. It is therefore understood that within the scope of thefollowing claims, the invention may be practiced otherwise than asspecifically described or exemplified herein.

1. A process comprising regenerating a used ionic liquid catalyst, recovering conjunct polymer from the regenerated catalyst and using at least a portion of the conjunct polymer.
 2. The process of claim 1, wherein the conjunct polymer is hydrogenated.
 3. The process of claim 1, wherein the conjunct polymer is dechlorinated.
 4. The process of claim 1, wherein the conjunct polymer is used to produce a hydrocarbon product.
 5. The process of claim 1, wherein the conjunct polymer is used to produce a fuel.
 6. The process of claim 1, wherein the conjunct polymer is used as a high energy content blending component in distillate fuel.
 7. The process of claim 1, wherein the conjunct polymer is used to produce diesel fuel.
 8. The process of claim 1, wherein the conjunct polymer is used to produce jet fuel.
 9. The process of claim 2, wherein the recovered conjunct polymer is hydrogenated using a hydrotreating catalyst comprising at least one Group VI or VIII metal and their combinations dispersed on a porous high surface area support.
 10. The process of claim 9, wherein the hydrotreating catalyst is selected from the group consisting of palladium on carbon, palladium on alumina, NiMo on alumina, CoMo on alumina, and NiW on alumina.
 11. The process of claim 3, wherein dechlorination is conducted by treatment of the recovered conjunct polymer with hot caustic.
 12. The process of claim 10, wherein the hot caustic comprises a metal hydroxide solution selected from the group consisting of NaOH, KOH, CsOH, RbOH, Mg(OH)₂, Ba(OH)₂ and their mixtures.
 13. A hydrocarbon product composition comprising conjunct polymer recovered from used ionic liquid catalyst.
 14. The composition of claim 13, wherein the hydrocarbon product is selected from the group consisting of lubricants, distillate fuel, diesel fuel, and jet fuel.
 15. The composition of claim 13, wherein the conjunct polymer has been treated.
 16. The composition of claim 13, wherein the conjunct polymer has been treated to remove chlorine or sulfur. 